Methods Improving HIV Protein Expression: Cell Substrate and Protein Purification: There is an urgent need to have multiple HIV envelope immunogen components for use in HIV vaccine clinical studies. Results of the RV144 vaccine clinical trial indicated that antibody responses to the gp120 Env proteins were the major components of the vaccine that contributed to the efficacy signal. In addition, the discovery of both broad and potent neutralizing antibodies against the HIV envelope in HIV-infected individuals, provides additional evidence that the human immune system can respond effectively to the HIV envelope and so envelope could be the major component of an effective HIV vaccine. There is an urgency to evaluate alternative strategies and technologies capable for developing highly productive cellular substrates suitable for high yield GMP manufacturing of HIV antigens and reduced product development lead times. The goal is to support research to improve the expression yield in a specific cell culture system (i.e. CHO), and the purification yield using specific purification regimens designed for HIV envelope protein suitable for use as clinical immunogens.